I’m often asked by my clients to help them generate reports in ACT. The first thing I talk to them about is GIGO: garbage in, garbage out. Reports in ACT (or any software for that matter) are only as good as the information within ACT.
The best way to generate good reports in ACT is to make sure you schedule your calls, meetings and to-dos in ACT and then make sure you clear those activities once they have been completed. When you clear an item, a history is created which can then be reported on by ACT.